1. Field of the Invention
The present invention relates to a capacitive load driver and, more particularly, to a capacitive load driver having short circuit protection.
2. Description of the Related Art
When driving capacitive loads (in, for example, printhead applications), there exists a possibility that a capacitive terminal could become shorted to either supply or to ground. It is thus desirable that a capacitive load driver withstand the short circuit. It is further desirable for a device having several driver outputs to remain operational when any of the outputs is shorted to either the supply or to ground.
Heretofore, driver outputs have been protected against short circuits by adding active current limiting characteristics to the driver. Another manner of short circuit protection includes depending on the R.sub.DSon (resistance of the drain to the source of a field effect transistor, or FET, when on) of the output or depending on the B*I.sub.b (current gain of the bipolar transistor multiplied by the base current) for a bipolar output to limit the current. Such techniques, however, are high dissipation techniques that may either cause a device with multiple outputs to overheat or activate the thermal protection feature on an integrated circuit. When many outputs are driven by one driver device, it is desirable to have the majority of the outputs active while a few of the outputs are protected. Accordingly, a low dissipation technique is desirable to provide adequate short circuit protection.